判断下列序列是否是周期序列。若是，请确定它的最小周期。(1) (n)=Acos (dfrac (5pi )(8)n+dfrac (pi )(6))-|||-(2) (n)=(e)^j(dfrac (n)(8)-pi )-|||-(3) (n)=Asin (dfrac (3pi )(4)n+dfrac (pi )(3))